在那里，如果可使用C＃方法组什么好处？ [英] Are there any benefits to using a C# method group if available?

问题描述

当使用像一个处理列表与LT;串＆GT; 你可以写：

When dealing with something like a List<string> you can write the following:

list.ForEach(x => Console.WriteLine(x));

或者你可以使用的方法组完成相同的操作：

or you can use a method group to do the same operation:

list.ForEach(Console.WriteLine);

我preFER code的第二行，因为它看起来更清洁的我，但有什么好处呢？

I prefer the second line of code because it looks cleaner to me, but are there any benefits to this?

推荐答案

好吧，让我们来看看，看看会发生什么。

Well, lets take a look and see what happens.

static void MethodGroup()
{
    new List<string>().ForEach(Console.WriteLine);
}

static void LambdaExpression()
{
    new List<string>().ForEach(x => Console.WriteLine(x));
}

这被编译成以下IL。

.method private hidebysig static void MethodGroup() cil managed
{
    .maxstack 8
    L_0000: newobj instance void [mscorlib]System.Collections.Generic.List`1<string>::.ctor()
    L_0005: ldnull 
    L_0006: ldftn void [mscorlib]System.Console::WriteLine(string)
    L_000c: newobj instance void [mscorlib]System.Action`1<string>::.ctor(object, native int)
    L_0011: call instance void [mscorlib]System.Collections.Generic.List`1<string>::ForEach(class [mscorlib]System.Action`1<!0>)
    L_0016: ret 
}

.method private hidebysig static void LambdaExpression() cil managed
{
    .maxstack 8
    L_0000: newobj instance void [mscorlib]System.Collections.Generic.List`1<string>::.ctor()
    L_0005: ldsfld class [mscorlib]System.Action`1<string> Sandbox.Program::CS$<>9__CachedAnonymousMethodDelegate1
    L_000a: brtrue.s L_001d
    L_000c: ldnull 
    L_000d: ldftn void Sandbox.Program::<LambdaExpression>b__0(string)
    L_0013: newobj instance void [mscorlib]System.Action`1<string>::.ctor(object, native int)
    L_0018: stsfld class [mscorlib]System.Action`1<string> Sandbox.Program::CS$<>9__CachedAnonymousMethodDelegate1
    L_001d: ldsfld class [mscorlib]System.Action`1<string> Sandbox.Program::CS$<>9__CachedAnonymousMethodDelegate1
    L_0022: call instance void [mscorlib]System.Collections.Generic.List`1<string>::ForEach(class [mscorlib]System.Action`1<!0>)
    L_0027: ret 
}

注意方法组的做法是如何创建一个动作＆LT; T＆GT; 委托一次性使用和拉姆达前pression方法创建一个隐藏的匿名委托外地和不它内联初始化，如果必要的。在 IL_000a 的通知 brtrue 指令。

Notice how the method group approach creates an Action<T> delegate for one time use and the lambda expression approach creates a hidden anonymous delegate field and does an inline initialization of it if necessary. Notice brtrue instruction at IL_000a.

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